1. Field of the Invention
The present invention is directed to a process and device for the contact-free measurement of the thickness of a workpiece having first and second surfaces which are opposite and plane-parallel to each other by deflecting a portion of a laser beam in a step-wise fashion across each of the surfaces, sensing a reflected beam which follows a given path for each of the portions of the laser beam to determine the angle between an initial position of the portion of the laser beam and the position causing the reflected beam that is detected, calculating the distance of the point of reflection from a reference plane, and then using the distance of various points to determine the thickness of the workpiece.
2. Prior Art
A process for measuring the thickness of a workpiece utilizing a plurality of laser beams is disclosed in U.S. Pat. No. 3,802,774. In this patent, at least one laser is disposed on each side of the workpiece. Each laser is provided with an acousto-optical light deflector to deflect the beam emitted thereby in a stepped fashion over the surface of the workpiece where they are deflected in diffused fashion and are recorded by detectors which are arranged at a distance from the surface and can only receive light traveling along one given path. The dimension of the workpiece is determined from the time difference between the beginning of the deflection of each laser beam and the time of detecting the reflected beam.
A disadvantage of this measuring process is that two complete laser systems and two light deflectors are required. The measuring accuracy can be impaired by external influences in either of the two laser systems which are installed separately.